Python - move UV for selected items
It's all about context, at no point are you in the image editor. The same bpy.ops.transform.translate() is used in the 3d view and the image editor. Basically, you could just save the current area, switch to the editor, perform transforms and switch back. Granted, there are much more elegant ways to do this but for a 3 line hack, it works quite well.

import bpy

#+ grab the current area
original_area = bpy.context.area.type

scene = bpy.context.scene
for count, ob in enumerate(bpy.context.selected_objects):
    if ob.type == 'MESH':
        scene.objects.active = ob
        #+ switch to the image editor to perform transforms etc
        bpy.context.area.type = 'IMAGE_EDITOR'
        bpy.ops.object.mode_set(mode='EDIT', toggle=False)

        bpy.ops.mesh.reveal()
        bpy.ops.mesh.select_all(action='SELECT')
        #+ select the uvs
        bpy.ops.uv.select_all(action='SELECT')

        bpy.ops.transform.translate(value=(0.125, 0, 0), constraint_axis=(True, False, False))

        #+ return to the original mode where the script was run
        bpy.context.area.type = original_area
        bpy.ops.object.mode_set(mode='OBJECT', toggle=False)